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Applications of Thin Films in Metallic Implants
Published in Sam Zhang, Materials for Devices, 2023
Katayoon Kalantari, Bahram Saleh, Thomas J. Webster
In the dip-coating technique (Figure 10.2), the substrate is immersed in a solution containing hydrolysable metal compounds (or readily formed particles). Then, in a controlled atmosphere containing water vapor and at a particular rate, the substrate is withdrawn from the liquid. After substrate removal, a homogeneous liquid film is formed on the surface. Finally, after the elimination of volatile solvents and the chemical reactions that occur at room temperature, a thin film results on the surface of the substrate. The viscosity of the liquid and withdrawal speed can be used to control the coating thickness. This method can be utilized to coat the cylinder, flat plane, and complex geometries with a large surface. This technique is a reproducible method which is low-cost and simple. The dip coating technique has applications in both the laboratory and industry due to the low-cost equipment and raw materials used, its easy steps and the development of products with good quality [8, 10].
Hydrophobic and Hydrophilic Polymer Coatings
Published in Sanjay Mavinkere Rangappa, Jyotishkumar Parameswaranpillai, Suchart Siengchin, Polymer Coatings, 2020
Sanjay Remanan, Harikrishnan Pulikkalparambil, Sanjay Mavinkere Rangappa, Suchart Siengchin, Jyotishkumar Parameswaranpillai, Narayan Chandra Das
The dip coating method comprises of simple immersion and withdrawal steps. In this method, the substrate is immersed into the coating medium and, after a specified time, withdrawn from the medium at a predefined speed and the coated substrate is allowed to dry. It is a low-cost process in which the thickness can be easily adjusted. Coating medium, coating speed, viscosity, lift-off angle, surface tension, gravitational force, dwell time, and viscous drag can significantly affect the quality of the dip coating process. This process is widely used for the modification of fibers and objects with intricate structures, where a high production output is generally needed to regulate the uniform composition of the liquid mixture after a specified time (Gutoff and Cohen 2010; ten Elshof 2015; Wypych 2016).
Printing and Recent Developments
Published in Asis Patnaik, Sweta Patnaik, Fibres to Smart Textiles, 2019
Rasiah Ladchumananandasivam, Iris Oliveira Da Silva, Luciani Paola Rocha Cruz Barros, Elisângela Bezerra das Neves Holanda
Dip coating is a technique used to apply layers or films (usually polymeric) on the materials (Oliveira and Zarbin 2005; Nassar et al. 2003). In this process, the substrate to be coated is submerged perpendicularly within the solution containing the material of interest and then withdrawn at a well-defined rate under controlled temperature. The insertion and removal of the substrate in the solution must be performed in a constant manner and without any type of vibration or external interference, in order to guarantee the homogeneous deposition of the material of interest. The residence time of the substrate in the solution before its removal is also an important control factor. This means that in order to obtain quality layers, in addition to the characteristics of the substrate and the precursor solution (solvent, concentration, viscosity, type of precursor), it is necessary to use equipment that promotes the insertion and removal of the substrate with high stability, with fine speed control and free from vibration (Oliveira and Zarbin 2005). The thickness of the coating is mainly defined by the withdrawal rate, the solid content and the viscosity of the liquid.
Post-processing treatments to enhance additively manufactured polymeric parts: a review
Published in Virtual and Physical Prototyping, 2021
F. Tamburrino, S. Barone, A. Paoli, A. V. Razionale
In general, the coating thickness and surface profile are highly influenced by coating material properties, such as viscosity and surface tension. However, process parameters also play a significant role, such as immersion and withdrawal speeds in the case of the dip coating technique.
Powder mixed-EDM for potential biomedical applications: A critical review
Published in Materials and Manufacturing Processes, 2020
Md Al-Amin, Ahmad Majdi Abdul Rani, Abdul Azeez Abdu Aliyu, Muhammad Al’Hapis Abdul Razak, Sri Hastuty, Michael G Bryant
The stability of HAP coating is a crucial factor for potential bio-implant since phosphate-calcium occupies maximum portion of the bone and teeth and provides bioactive responses. Moreover, the properties of HAP coating such as mechanical strength, corrosion-resistant behavior, and biological response are affected by various surface treatment methods.[201] Although numerous techniques of apatite and Ca-P-based ceramics deposition on the biomaterials have been reported, researchers are trying to developing new methods, called PM-EDM, which is proposed as a potential manufacturing process of the bio-implants. The deposition techniques are classified into two groups: chemical and physical deposition processes. The physical modification technique includes thermal spraying methods, pulse laser deposition, laser surface alloying, laser melting deposition, spray pyrolysis technique, and sputtering process. On the other hand, the chemical deposition method represents the following: sol-gel, hot pressing, dip coating, electrochemical deposition, electrostatic spray deposition, and electrophoretic deposition.[38,201] Among them, the plasma spray technique is commercially used in the manufacturing plants for depositing Ca-P-based coating on the implants. However, plasma spray requires intense heat for a higher rate of coating and a new technique is demanded to eliminate the limitation of the formation of an amorphous coating.[212] The sol-gel technique is familiar due to following a simple procedure and being economical which can produce higher strength coating compared to the bio-mimetic coating process.[235] But this process is unable to generate a porous surface. The dip-coating technique offers several benefits including lower set up cost, easy to use, ability to coat complex and irregular shape, uniform coating, and lower operating temperature.[213] Although both the chemical and physical techniques offer some advantages, they have various drawbacks, as well over the coating processes, surface quality, coating compounds and thickness, and production costing. Table 11 shows the basic advantages and demerits of existing surface deposition techniques.
Graphene-based electrodes for ECG signal monitoring: Fabrication methodologies, challenges and future directions
Published in Cogent Engineering, 2023
Rimita Dey, Pravin Kumar Samanta, Ram Pramod Chokda, Bishnu Prasad De, Bhargav Appasani, Avireni Srinivasulu, Nsengiyumva Philibert
The stretchable and flexible electronics field has been getting huge attention from researchers recently. The continuous progress in this area has brought a revolution in medicine. The synthesis and processing of reproducible and consistent graphene is a huge problem for graphene-based ECG sensors and electrodes. Several advancements are required to control the graphene layer numbers, overcome mechanical restrictions, and construct devices with unique structures. In general, the wearable sensor consists of two major components- a) conductive mesh, which captures the signal, and b) stretchable/flexible substrate, which protects the conductive mesh and offers stretchability/flexibility to the sensor. Hence, the sensor materials are selected wisely, and the structures are designed carefully not to compromise the sensor’s performance. Although the graphene-based electrodes are flexible, stress corrosion cracking (SCC) might still appear on the graphene layer due to several environmental conditions during ECG monitoring. This may cause an increase in electrode impedance, causing degradation of the quality of the acquired signal. This review paper discusses a comparative study of several techniques and procedures for fabricating graphene-based ECG electrodes. The methods are screen printing, dip coating, wet transfer, wet transfer and dry patterning, spray coating, spin coating, drop casting, inkjet printing, electrospinning etc. Mechanisms of all procedures are described along with illustrations, merits- demerits and feasibility in manufacturing. Screen printing is simple and cost-effective, but has limited resolution. Dip coating is easy to control thickness and uniformity but is not very scalable. Drop casting is simple and low-cost, but it also has limited scalability. Wet transfer offers high-quality graphene and large-area deposition but requires expensive equipment and a complex process. Electrospinning is versatile and scalable, but has limited resolution. Dry patterning offers high resolution and precise control of electrode shape and size, but is complex and not very scalable. Spin coating is simple and low cost but has limited scalability and is difficult to control thickness and uniformity. Spray coating offers large-area deposition and high-quality graphene, but requires expensive equipment and a complex process. Inkjet printing is material-conserving and has a high resolution, but it is limited in scalability and requires specialised ink. Many researchers have already paid attention to this, but further research is required.